STUDY  OF  ANODES  IN  ELECTROLYSIS  OF  COPPER 
LEACHING  SOLUTIONS  CONTAINING 
CHLORIDES 


BY 


LOUIS  F.  STUEBE 


THESIS 


FOR  THE 

DEGREE  OF  BACHELOR  OF  SCIENCE 

IN 

CHEMICAL  ENGINEERING 


COLLEGE  OF  LIBERAL  ARTS  AND  SCIENCES 

UNIVERSITY  OF  ILLINOIS 


1922 


Digitized  by  the  Internet  Archive 
in  2015 


https://archive.org/details/studyofanodesineOOstue 


ACKNOWLEDGMSITT 


I acknowledge  man’r  suggestions 
and  muoh  aid  in  this  work  to  the  directions  of 
, Dr,  W.  S.  Putnam 


STUDY  ANODES  IN  ELECTROLYSIS  OP 


COPPER  LEACHING  SOLUTIONS  CONTAINING  CHLORIDES 

Part  I 

Introduotioii 

This  work  is  interested  in  the  study  of  the  corrosive 
effects  of  copper  leaching  solutions  containing  chlorides 
upon  the  anode  during  electrolysis. 

Many  copper  ores  are  more  economically  leached  and 
electrolyzed  directly  from  the  leaching  solution  than  by 
roasting,  smelting,  and  subsequent  electrolysis.  In  fact 
there  is  reason  to  believe  that  in  the  future  almost  all 
ores  that  show  this  advantage  will  be  eleotrolyged,  there- 
by eliminating  the  great  outlay  in  smelting  plant  and  the 
great  cost  of  fuel.  Moreover  the  whole  process  will  be 
entirely  under  the  control  of  the  mine  operator,  who  will 
not  have  to  ship  his  matte  to  the  refineries  and  depend 
upon  them  for  the  speed  of  his  turnover. 

The  requirements  of  a plant  for  the  electrolysis 
of  copper  leachings  would  be  a choice  of  the  various  leach- 
ing processes  of  which  there  are  now  several  rather  high- 
ly developed,  and  a dependable  scource  of  electrical 
current  which  is  easily  obtained  in  our  mountains  from 
hydro-electric  stations.  The  other  requirement,  which 
is  the  primary  one  and  has  thus  far  probably  been  the  chief 
cause  for  the  reluctance  of  operators  to  establish  it,  is 
the  electrolysis  process  itself;  which  means  the  study  of 
the  character  of  the  leac^^ing  solution,  the  control  of  the 


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current,  and  the  type  of  anode. 

This  problem  is  primarily  ooncerned  with  the  study  of 
the  anode  when  the  analysis  shows  the  presence  of  chlorides. 

In  this  thesis  the  work  has  been  carried  to  the  study 
of  iron  alloy  oxides  only  as  the  author  was  unexpectly  halted 
in  his  work.  However  as  the  preliminary  study  has  covered 
the  field  of  all  types  of  anodes  in  general  and  their 
probable  development  to  obtain  the  desired  non-corrosive 
anode  for  copper  chloride  solutions,  and  to  assist  any  who 
may  continue  this  study,  he  has  included  in  the  history  and 
conclusion  such  information  as  he  has  considered  of  value 
in  the  continuation  of  this  study. 


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Part  II 
History 

I'he  oorrosion  of  all  anodes  in  oopper  electrolysis 
is  imown  to  be  an  unavoidable  loss.  I’o  be  sure  the  ideal 
anode  would  be  an  absolutely  non-corrosive  one.  However 
among  anodes  there  is  a big  difference  in  the  degree  of 
solubility  of  the  same  in  their  electrolytes,  consequent- 
ly when  an  anode  shows  little  corrosion,  as  lead  in  copper 
sulPhate  solution,  it  is  termed  as  non-corrosive.  Again 
an  anode  may  be  non-corrosive  in  one  electrolyte  and  be 
quite  corrosive  in  an  electrolyte  of  slightly  different 
composition.  In  addition  the  efficiency  of  the  process 
depends  upon  the  character  and  temperature  of  the  electro- 
lyte, the  current  density,  and  the  voltage;  all  of  which 
must  be  considered  along  with  cost  of  anodes  in  determining 
the  economical  value  of  a given  process, 

These  are  the  conditions  which  contribute  to  the 
complications  involved  in  the  study  of  anodes  in  electroly- 
sis of  copper  leachings. 

The  industrial  electrolysis  of  copper  leaching  solu- 
tions is  in  general  this; 

The  copper  ore  composed  of  ohalcocite,  azurite, 

malachite,  along  with  other  minerals,  is  first  crushed  fine 

1. 

in  rolls  and  roasted  as  in  the  Laszczynshi  process.  Then 

it  is  leached  with  dilute  sulphuric  acid,  or  with  dilute 

sulphuric  acid  and  ferric  sulphate  solution  as  in  the 
2 

Siemens-Halske  process.  Consequently  the  leachings  contain 
copper  sulphate,  ferrous  sulphate,  ferric  sulphate,  acid. 


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and  other  impurities. 

The  copper  leaohings  are  then  introduced  into 
wooden  vats,  many  of  which  are  lined  with  pitch  or  asphalt. 
These  vats  vary  in  design  and  capacity,  but  an  average  may 
be  taken  as  4-|-  feet  deep,  3^  feet  wide,  and  6 feet  long. 

The  leaohings  are  run  in  by  a circulation  method,  that  is, 
the  solution  runs  from  vat  to  vat  by  gravity,  varying  in 
concentration,  or  it  is  electrolyzed  in  one  vat  until  de- 
pleted of  copper.  After  this  the  liquor  is  sent  back  to 
act  as  new  leaching  solution.  Generally  in  either  case 
some  means  of  maintaining  circulation  is  employed.  This 
is  occasionally  done  mechanically,  by  flow  of  electrolyte, 

or  by  bubbling  gas  through  the  solution  as  is  done  in  the 
5 

Carmichael  process,  in  which  SOg  is  passed  through  not  only 
for  stirring  but  also  to  furnish  fresh  sulphuric  acid  and 
assist  at  depolarization. 

The  cathodes  are  copper  sheets  about  l/32  inch 
thick  and  by  3 feet  with  a heavy  cross-bar  across  the 
top  as  contact  arms.  They  are  generally  given  a thin  coat 
of  glue  or  engine  oil  before  being  started  in  order  to  give 
a uniform  and  well  adhering  plate. 

The  anodes  are  of  various  material  and  measure 
the  same  as  the  cathodes  except  that  they  have  varying 
thicimesses.  They  also  have  a strong  contact  bar  across 
the  top. 

Along  the  upper  edge  of  each  of  the  two  long 

sides  the  vats  have  heavy  copper  bus-bars  to  make  contact 
with  the  cross  contact  bars  of  the  cathode  and  anode.  One 


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is  positive  and  the  other  negative,  and  are  so  arranged  that 
the  positive  makes  oontaot  with  the  anode,  and  the  negative 
with  the  cathode. 

2he  ordinary  voltage  for  simple  sulphate  leach- 
ing solution  is  2.2b  to  2.b0  volts,  and  the  current  densi- 

4 

ty  is  18  to  20  amperes  per  square  foot  of  cathode  surface. 

The  corrosion  of  anodes  in  general  is  quite  well 

understood  in  the  electrolysis  of  copper  sulphate  solutions 

1 2 

as  used  in  the  Laszczynski  or  Sieman-Halske  processes.  In 
fact  the  process  is  very  simple  when  no  iron  is  present,  in 


which  case  lead  anodes  are  used  to  the  greatest  advantage. 

However  in  the  presence  of  iron  sulphate  some  handi- 
caps arises  from  the  polarization  of  the  ferrous  and  ferric 
ionS.  i’or  best  results,  control  of  the  ferric  sulphate 
concentration  is  essential  as  this  impurity  reduces  current 
efficiency,  causes  poorer  deposition  of  copper,  and  when 

the  copper  concentration  becomes  low  in  the  presence  of  iron 

6 

sulphate,  an  additional  decrease  in  effioi^^oy  observed. 

The  lowering  of  efficiency  is  due  to  the  solvent  action  of 

7 

ferric  sulphate  upon  the  deposited  copper.  regener- 

ated sulphuric  acid  or  ferric  sulphate  solution  is  used  over 

and  over  again,  the  ferric  sulphate  becomes  so  concentrated 


7 

that  soon  all  the  copper  is  redissolved.  Thus  ordinary 
resolution  at  the  cathode  is  2%;  but  when  ferric  sulphate 
reaches  the  concentration  of  2b>,  it  will  corrode  cathode 
copper  to  such  an  extend  that  8 amperes  will  be  required 

a 

to  merely  replace.  The  formation  of  ferric  sulphate  is 


prevented  by  inclosing  the  anode  in  porous  material  to 


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prevent  transference  of  ferric  ions;  thus  tight  fitting  bags 

are  frequently  used,  the  thicioaess  of  the  cloth  varying 

7 

inversely  as  the  strength  of  the  current. 

This  illustrates  the  disadvantages  of  iron  in  the  elec- 
trolyte, a metal  which  is  present  in  all  copper  leachings. 
Nevertheless  lead  anodes  are  used  the  same  as  in  simple 
copper  sulphate  solution,  the  lead  anode  merely  peroxidizes 
and  sulphatizes  slowly  as  it  is  slightly  attacked  by  the  free 

a 

oxygen  and  the  sulphate  radicle. 

But  when  chlorides  are  present,  lead  will  no  longer 
serve  as  anode  as  corrosion  is  too  rapid.  Chlorides  have 
a corrosive  effect  which  is  little  understood  electrochem — 
ically  or  otherwise,  and  as  valuable  copper  leaching  solu- 
yions  are  known  that  contain  chlorides  in  considerable 
amount  which  can  not  be  removed  to  any  advantage,  it  be- 
hooves the  metallurgist  of  plants  having  such  leachings  to 
find  a non-corrosive  anode  which  is  econoijdioal  enough  to 
put  this  copper  on  a competitive  market  with  copper  from 
copper  sulphate  leachings. 

As  an  examination  of  the  literature  shows  that  chlo- 
rides in  copper  leaching  solutions  are  considered  as  merely 
to  be  avoided,  and  no  strictly  theoretical  explanation  has 
been  made  for  the  apparent  cause  why  these  solutions  be- 
have so  much  different  from  sulphate  solutions,  the  author 
has  had  reference  only  to  such  practical  work  as  has  been 
experimentally  undertaken  from  time  to  time  to  solve  this 
problem. 


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9 

2he  Hoepfner  process  using  leachings  containing 

cuprous  chloride  has  been  developed.  It  uses  two  coropart- 

ments,  anode  and  cathode,  each  containing  the  leachings, 

and  for  an  anode  uses  carbon.  The  two  compartments  are 

separated  by  a permeable  diaphragm.  However  it  has  been 

found  unsuccessful  on  account  of  the  short  life  of  the 

diaphragm  and  the  corrosion  of  the  carbon  anodes. 

When  leaching  solutions  contain  chlorides,  fused 

magnetite  or  ferro-alloys,  generally  ferro-silicon,  is  now 

used*  Where  an  efficient  depolarizer  is  employed,  besides 

3 

the  materials  mentioned  above  carbon  may  be  used,  however 

depolarization  must  be  complete. 

10 

The  Chile  ]jlzploration  Co.  used  fused  magnetite  anodes 

in  their  South  American  plant  in  a leaching  and  chlorination 

process  until  no  more  could  be  purchased  from  Germany.  In 

their  research  department  at  Perth  Amboy,  IT.  J.  they  found 

th©  best  substitute  to  be  Ibyi  ferro-silicon  or  ’’duciron”. 

This  is  not  as  good  as  magnetite, as  found  by  use  in  their 

10,000  ton  plant,  as  it  required  Ibfi  more  energy  and  raised 

the  temperature  too  high  for  the  asphalt  insulation  that 

11 

was  used  in  the  vats.  Later  Colin  G.  Pink,  now  director 
of  the  Chile  Exploration  Co.,  said  that  13‘4  ferro-silicon 
has  been  found  superior  to  lead  and  magnetite  as  an  insol- 
vent anode  in  electrolytes  containing  not  only  sulphuric 
acid,  but  also  nitric.  Although  no  mention  is  made  of 
chlorides,  the  statement  of  being  successful  in  nitric  acid 
may  be  taken  as  meaning  hydrochloric  as  well.  He  goes  on  to 
say  that  next  to  ferro-silicon,  the  ferro-chromes  are 


r 


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8 - 

industrially  important  as  non-corrosive  alloys.  However, 
although  chemically  corrosion  proof,  they  are  not  very 
electrolytically  corrosion  proof.  He  says  that  60>i  chrom- 
ium and  iron  is  the  best, and  in  addition  that  niciel- 
chrome  alloys  are  becoming  popular. 

However  a recent  letter  received  in  the  spring  of  1922 
from  the  U.  S,  Hureau  of  Mines  by  the  Division  of  Applied 
Chemistry  of  the  University  of  Illinois,  stated  that  although 
f erro-silicon  alloys  have  been  found  the  most  satisfactory 
anodes  in  the  electrolysis  of  copper  ores  containing  chlor- 
ides, yet  the  results  were  far  from  being  successful,  and 
said  that  research  in  this  direction  should  be  encouraged. 

Consequently  the  author  started  this  work  under  the 
directions  of  Asst.  Prof.  Putnam, 


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Part  III 
Experimental 

It  was  decided  to  investigate  the  subject  of  anodes 
thoroughly  and  particularly  along  the  line  of  alloy  steels 
of  various  compositions* 

The  study  of  niciiel  was  first  undertaken  as  several 
specimens  of  this  alloy  of  varying  composition  were  on  hand. 
This  was  to  be  followed  by  work  om  ferro-chromes,  and  pos- 
sibly aluminium  alloys.  Ferro-silioons  were  only  to  be 
QO^sidered  in  special  forms  as  the  oxides  as  it  was  felt 
that  the  pure  alloys  have  been  fairly  well  investigated. 

It  developed  that  time  was  only  available  to  inves- 
tigate the  nicxel  alloy  to  the  extend  herewith  set  forth. 

All  investigation  were  conducted,  on  the  oxidized 
alloy.  The  variable  factors  were  these: 

Oomposition  of  alloy 
Method  and  time  of  oxidation 
Voltages  and  currents 

The  solution  used  was  considered  representative  of 
such  solutions  found  in  the  leaching  of  copper  ores  con- 
taiming  chlorides.  It  was  this; 

Solution  #1 

( S^/i  OuS04‘*5H20  - 100.0  gm. 

'&]•  O u ( 

( OuClg  - 10.6  ” 

If.  Fe  FeSO^  - 27.1 

H HOI  - 1^.5  cc. 

Tater 


To  make  one  liter 


».  r.f 


1.  V ■ '■  .’«r  ■ : 

■.--....  N • ' ,:?iX.r;  i'  -.ri-.' 

. I ' w.'rir,  vi-(  XX 

: . ••  i ’..•!**  <t*  . .CXi^ 


10 


12 

The  raethod  of  applying  an  oxide  ooating  was  this: 

, nitwe 

Eq.ua!  parts  of  sodium  and  potassiumy^were 

placed  in  an  ii^on  crucible,  melted  and  superheated  to  bOO 
degrees  Oentigrade,  when  black  oxide  of  manganese  was  added, 
one  part  to  fifty  by  volume,  and  then  the  superheating 
continued  to  bOO  degrees  Oentigrade.  The  alloy  anode  was 
thoroughly  cleaned  by  burnishing  and  a thin  coat  of  lubri- 
cating oil  applied.  This  was  then  dipped  directly  in-to 
the  molten  bath  for  a variable  period.  It  wqs  then  quenched 
in  cold  water  and  heated  in  boiling  water.  Then  it  was  dip- 
ped in  a hot  heavy  lubricating  oil  at  about  200  degrees  to 
remove  all  traces  of  water.  When  the  anode  was  to  be  used, 
it  was  boiled  in  a dilute  solution  of  potassium  hydroxide 
to  remove  the  adhering  oil,  rinsed  in  water,  and  dried. 

The  coating  was  a jet  black  oxide. 

The  first  experiments  were  conducted  on  5'/*  nickel- 
steel  as  a short  preliminary  experiment  on  nickel-steel 
showed  little  encouragement . The  final  experiments  were 
conducted  upon  nickel-steel. 

In  each  case  solution  #1  was  used,  copper  foil  for 
cathode,  and  the  distance  between  anode  and  cathode  was 
maintained  the  same  in  all  oases  at  2 inches.  The  current 
was  controled  by  a resistance  reostat  in  the  line,  and  a 
carbon  block  resistance  in  parallel  with  the  cell.  The 
voltage  in  ail  cases  was  maintained  constant,  and  with  this 
factor  constant  it  will  be  seen  that  any  variation  in 
amperage  in  the  various  runs  was  due  to  vaa^tion  in  the 


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11 


degree  ol  resistance  of  the  anode  surfaces,  'fhe  solution 
was  not  circulated  or  replenished,  but  was  run  to  a fair 
exhaustion  of  the  copper.  Temperature  was  room  temperature. 

}ixperiment  fl 

Solution  -jtl  5%  Hi-steel,  oxidized  3 min. 

Voltage  maintained  at  three  volts. 

Amperage  as  shown  in  Tab.  I , and  figurell, 
pp.  12  and  13  respectively. 

Exp • #2 

Solution  #1  Hi- steel,  oxidized  10  min. 

Voltage  maintained  at  2.b  volts. 

Amperage  as  shown  in  Tab.  I,  and  fig.  I. 

Exp.  #3 

Solution  fl  5/i  Hi-steel,  oxidized  10  min. 

Voltage  maintained  at  2.0  volts. 

Amperage  as  shown  in  Tab.  I,  and  fig.  I. 

Erom  the  tables  and  graph  it  is  seen  that  the  IQ  minute 
oxidation  made  it  possible  to  have  the  same  amperage  at  a 
lower  voltage,  2.b  volts,  as  compared  to  3 volts  for  the 
3 minute  oxidation.  Also  the  flatter  curve  shows  it  to  be 
more  constant  and  able  to  maintain  itself  better. 

The  10  minute  oxide  at  2 volts  and  2.1  ampere  shows 
the  best  result  on  this  alloy  and  its  observations  are 
noted  in  the  tables. 

Corrosion  of  the  anode  in  each  case  was  quite  Uniform 

and  deep  beyond  the  point  to  classify  them  as  non-corrosive . 

one  encouragement  was  the  lov;  voltage  at  which  a 


r 


♦ 


•'<.  ‘ 1' 


I • ■ 

■/■jt«  -#.h  ^ 


v‘»vu;  '.ti 


12 


Tables  I 


S/4h  Ui-steel 

Solution  fl 

Constant  Voltages 

Time 

]?jxp.  jfl  ij;xp.  if-2 
3 volts  2^  volt 
current  in 

ii:xp.  f3 
s 2 volts 
amperes 

Observations  on  ijjxp,  f3 

0 

.30 

.30 

.21 

Ho  gas  evolved  at  anode. 

15 

.35 

.30 

.25 

30 

.37 

.30 

.28 

46 

.37 

.31 

.30 

Cu  begins  to  deposit  on 

60 

.39 

.33 

.32 

anode. 

75 

.43 

.37 

. 36 

Scales  begin  to  form  on 

90 

.49 

.42 

.41 

anode. 

105 

.62 

.47 

.43 

120 

.74 

.52 

.43 

135 

.79 

.55 

.43 

cu  on  oathode  deposits 

150 

,85 

.58 

.47 

rapidly. 

Cu  on  oathode  becoming 

165 

.93 

,60 

.48 

spongy. 

Oas  begining  to  come  off 

180 

1.00 

.63 

.48 

cathode . 

195 

1.03 

.68 

.49 

210 

1,06 

.75 

.50 

spongy  cu  on  cathode 

225 

1.07 

.76 

.50 

forming  very  rapidly. 

240 

1.06 

.77 

.57 

considerable  gas  being 

2oO 

1.05 

.77 

. . .58 

evolved  at  catihode. 

XI  i 'j 


V'J 

V 


).utT 


-•i  r.  o. 


1. 


I* 


13 


li’igure  I 


14 


strong  flow  of  current  may  be  maintained,  thereby  showing 
an  improvement  over  lead  or  ferro-silicon,  as  well  as 
magnetite  anodes  in  efficiency. 

Oonsequently  30‘>  ITi-steel  was  experimented  upon.  !I!hese 
specimens  were  about  one-half  the  size  of  the  lli-steel, 
and  the  oxidation  was  done  thus; 


Sxp,  j 

^ 6 7 

8 y 

10 

11 

IS 

Time 

8-8  7-7 

6-6  5-5 

18 

15 

IS 

The  double  numbers  indicate 

that  the 

anode 

was  oxi 

dized 

for  two  periods 

each  of  the 

length  of 

time 

given. 

The  amperage  variations  for  all  of  the  double  oxida- 
tions, or  Sxp,  f6,  7,  8,  and  9,  are  given  in  Tab.  II,  page 
15,  and  on  fig.  II,  page  17, 

Experiment  8 gave  the  best  results, and  observations 
for  it  are  noted  in  Tab,  II. 

It  will  be  noted  that  by  double  oxidation  it  was 
possible  to  maintain  a current  density  of  one  ampere  for 
some  time. with  two  volts. 

The  corrosion  was  quite  pronoumced,  but  for  the  much 
smaller  area  the  results  were  much  better  than  with  5fg 
Ni-steel,  The  most  noteworthy  result  was  that  the  oxide 
surface  showed  pronounced  evidence  of  protecting  the  lower 
area  in  sections, 

incidentally  it  should  be  mentioned  that  it  was  ob- 
served when  drilling  the  holes  for  the  contact,  that  the 
highest  oxidized  specimens  were  soft  on  the  surface  and 
very  hard  in  the  center.  This  was  probably  due  to  the 
heat  treatment  of  the  metal  during  oxidation. 


( 


t 


T 


5'  C 


M r 


30;i  Ni- 

■steel 

- 15  - 

Tables  II 
Solution  #1 

Constant  Volts,  2 v. 

Time 

Exp. #6  Bxp.#7 

Exp. #8  Exp. #9 

min. 

Current  in 

amperes 

Observations  on  Exp.  #8. 

oO 

.10 

.10 

.10 

.10 

Slight  evolution  of  gas  at 

2 

.10 

.10 

.10 

.10 

anode • 

4 

.10 

.10 

.10 

.10 

6 

.10 

.10 

.10 

.10 

8 

.10 

.10 

.10 

.10 

10 

.12 

.10 

.10 

.10 

12 

.16 

.10 

.10 

.10 

14 

.19 

.10 

.10 

.10 

16 

.20 

.10 

.10 

.10 

18 

.21 

.10 

.10 

.10 

20 

.21 

e 

O 

.10 

.10 

22 

.22 

.10 

.10 

.10 

24 

.24 

oil 

.10 

.10 

26 

.26 

.12 

.10 

.10 

Evolution  of  gas  decreases. 

28 

• 26 

.13 

.11 

.10 

30 

.27 

.14 

.11 

.10 

32 

.28 

.15 

.12 

.12 

Gras  evoluti  on  stopped. 

34 

.28 

.16 

.12 

.13 

36 

.29 

.13 

.14 

38 

.30 

.17 

.13 

.16 

40 

.34 

.18 

.14 

.17 

42 

.36 

.18 

.14 

.18 

44 

.37 

.19 

.15 

.18 

46 

• 39 

ol9 

ol5 

.18 

- 16  - 

Tables 

II 

Time 

#6 

#8 

#y 

Observations  on  Bxp,  jfSm 

48 

• 40 

.20 

.15 

.19 

50 

.40 

.20 

.15 

.19 

55 

.42 

.22 

.16 

.22 

60 

.43 

.23 

ol7 

.24 

65 

.44 

o25 

.18 

.26 

70 

• 45 

.27 

.20 

.29 

Flaking  on  anode  begins. 

85 

.44 

.31 

.25 

.35 

100 

.44 

.35 

.28 

.40 

Ou 

begins  to  j^eposit  on  anode 

115 

.44 

. 36 

.30 

.41 

■^130 

o44 

.37 

.31 

.40 

145 

.43 

.37 

.32 

.40 

160 

.43 

.37 

.32 

.39 

Ou 

dep.  on  cathode  becoming 
crystaline. 

175 

.43 

.36 

.32 

.38 

Gu 

dep.  on  anode  becoming 
crystal ine . 

lyo 

.42 

.36 

.32 

.37 

2q5 

.41 

.35 

o32 

.37 

220 

.40 

.35 

.36 

235 

O 

o 

.35 

.32 

250 

.40 

.34 

o35 

265 

.39 

.33 

.30 

OU 

dep.  becoming  spongy. 

280 

.39 

.33 

.33 

295 

.39 

.32 

.27 

310 

.39 

.32 

.32 

325 

.38 

.32 

.26 

340 

.38 

.31 

.30 

355 

.38 

.25 

370 

.37 

.31 

.28 

17 


Figure  II 


T//ne  E/apsed-^  Minutes 


18 


From  the  durves  it  will  be  seen  that  there  is  a reduction 
in  amperage  down  to  the  6-6  minute  anode  when  the  results  a- 
gain  show  the  tendency  to  a higher  current. 

Thus  it  may  be  concluded  that  for  30^*  ITi-steel,  and 
double  oxidation,  that  two  6 minutes  of  oxidation  is  the 
best , 

For  the  single  oxidation,  that  is  for  Exp.  #10,  11, 
and  12,  the  results  are  given  in  Tab.  Ill,  page  19,  and 
fig.  Ill,  page  21. 

Here  the  amperage  was  double  as  compared  to  Exp. 

#6,  7,  8,  and  9 for  the  same  voltage,  showing  much  less 
resistance  in  the  oxide  oaating. 

Again  there  is  observed  a minimmn  amperage  when 
oxidized  for  one  15  minute  period. 

As  Exp.  #11  showed  the  best  results,  the  observations 
noted  in  Tab.  Ill  are  upon  this  anode. 


* r.“ 


19 


Tables  III 

3Of0  Ni-steel  Solution  jpl  Constant  Voltages  2 v. 


Time 

Sxp.flO  Bxp 

••#11 

Exp. #12 

min 

• 

Current 

in 

amperes 

Observations  on  Exp.  #11 

0 

.20 

.20 

.20 

ITo  evolution  of  gas. 

2 

.22 

.22 

,22 

4 

.23 

.24 

.24 

6 

.24 

.26 

.26 

8 

.24 

.26 

.28 

10 

.25 

.27 

.29 

12 

* 

OD 

.27 

o30 

14 

.32 

.28 

.31 

16 

.35 

.28 

.31 

Flaking  of  anode  surface 

begins. 

18 

.37 

.28 

.32 

20 

.38 

.29 

.33 

22 

.40 

o30 

.33 

24 

.41 

.32 

.36 

26 

.42 

.33 

.36 

28 

.42 

.34 

.37 

Cu  begins  to  dep.  on  anode 

30 

.43 

.34 

o38 

32 

.43 

.35 

.38 

34 

.43 

.35 

.39 

36 

.44 

.36 

.40 

38 

.44 

.35 

.40 

40 

•44 

.36 

.40 

46 

.44 

.37 

.40 

50 

.43 

.38 

.40 

65 

.43 

.38 

.41 

ft 


- 20 

- 

Tables 

Ill 

Time 

#10 

#11 

#12 

Observations  on  Exp.  #11. 

60 

.43 

.38 

o41 

Cu  on  anode  becomes  cryst. 

70 

.43 

.39 

.41 

80 

.42 

.39 

.41 

90 

.42 

o39 

.42 

100 

.42 

.39 

.42 

110 

o41 

.38 

.43 

120 

.41 

.38 

.43 

Ou  on  cathode  becomes  cryst 

130 

.40 

.38 

140 

.39 

o37 

.43 

160 

.39 

.37 

160 

.39 

.36 

.43 

170 

.39 

.36 

180 

.40 

.35 

.42 

190 

.40 

.34 

.42 

200 

.40 

.34 

.42 

I 


4 


Figure  III 


T/me  £ lapsed  '^m/tri/tes 

80  /zo  uo  zrao 


22 


Part  IV 
Conolusions 

As  will  be  seen  the  results  were  not  suocessful  as 
to  producing  a new  anode.  However  they  are  conclusive  in 
the  study  of  the  oxide,  effect  of  time  and  method  of 
oxidation,  and  effect  of  voltage  and  current  density.  Thus 
these  results  may  be  used  in  the  further  study  of  the  anode 
especially  in  terms  of  oxide  coatings. 

It  was  observed  that  the  higher  Ni-steel  alloy  showed 
less  corrosion  and  a greater  adaptibility  to  take  on  a 
protective  coating  of  oxide  as  shown  by  lower  amperage  and 
corrosion  of  anode. 

That  double  oxidation  gives  better  coatings  than 
single  oxidation  as  shown  between  the  amperages  in  Tab. 

II' and' III. 

That  a minimum  amperage  may  be  obtained  for  a given 
alloy  by  oxidizing  for  a certain  length  of  time,  either 
for  double  oxidation  or  single  oxidation  as  shown  by  curves 
on  fig.  II  and  III. 


.J 


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v^trl  fif'. 

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t'.i.T. 

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Ca 


- 23  - 

Part  V 
Suggestions 

Better  results  may  be  obtained  by  hammering  the  anode 
as  it  is  withdrawn  at  the  red  heat  from  the  niter  bath, 
then  after  sufficient  treatment  in  this  way  it  should  be 
given  a final  bath  without  hamraering.  The  theory  is  to 

get  the  oxide  ooating  as  dense  as  possible. 

Another  attempt  would  be  the  fusion  of  the  oxide 

coating  if  possible  by  heating  to  the  fusion  point  of  the 

oxide.  This  would  tend  to  approach  the  quality  of  fused 

magnetite  mixed  with  nicxolous  oxide* 

Also  similar  tests  should  be  run  on  ferro-chrome  and 

ferro— silicon  alloi^®  with  oxide  coating. 

The  study  of  aluminium  alloys  seems  plausuble  due  to 

the  low  position  of  aluminium  in  the  electromotive  scale. 

Also,  if  available,  experiment  should  be  made  on  a 

13 

nevi/  alloy  developed  in  Italy,  imown  as  biaAmetal.  The 


approximate  composition  is  this 

Metal  Kange  Average 

Copper  35-44%  40% 

Iron  1.6-4.76  3 

Tungsten  3-6  3 

Nickel  60.6-46.25  54 


Acid  resisting  qualities  are  these: 

Sulphuric  any  strength  under  100  degrees  Cent. 
Hydrochloric  ” ” ” any  temperature. 

Acetic  ” " '*  " " 

Citric  ” 


24 


Tannio  any  strength,  any  temperature 
Cold  nitrio  up  to  1.40  SP.  gr. 


25 


Part  VI 
Bibliography 

1.  Hoffman,  Metallurgy  of  copper,  1915  HcL.,  p.414 

2.  ” , " p.430 

3.  Lawrenoe  Addicts,  Chem,  & Met,,  Vol.23,  p.llO 

4.  ” ’’  , ” ” ” .,  Vol.23,  p.275 

6,  Hoffman,  Metallurgy  of  Copper,  1915  Bd.,  p,415 

6.  iSdw.  p,  Kern,  Chem.  & Met.,  Vol.18,  p.507 

7.  Hoffman,  Metallurgy  of  Copper,  1915  Ed.,  p.415 
B.  P.  L.  Antisell,  Chem.  & Met.,  Vol.18,  p.423 

9.  Hoffman,  Met.  of  Copper,  1915  Ed.,  p,434 

10.  E.  A.  Cappelen  Smith,  Chem.  & Met.,  Vol.16,  p.l62 

11.  Colin  (j.  rink,  Chem.  & Met.,  Vol.23,  p.471 

12.  Sidney  Cornell,  Chem.  & Met.,  Vol.24,  p301 

13.  Arrigo  Tedesoo,  Cheiji.  & Met.,  Vol  23,  p.847 


26 


Part  YII 


Index 

iJibliography 

p . 25 

Oonolusions 

22 

Experimental 

9 

Pigure  I 

13 

Figure  II 

17 

Figure  III 

21 

History 

3 

Introduction 

1 

Suggestions 

23 

tables  I 

12 

tables  II 

15 

Tables  III 

19 

